Polychlorinated biphenyls (PCBs) and petroleum hydrocarbons (PHs) frequently co-contaminate aquatic sediments found at Superfund sites. Components of these complex and toxic mixtures bioaccumulate in the food chain eventually threatening human health. Microbial degradation of PCBs and PHs is often slow or inhibited by environmental conditions or the contaminants themselves. In fact, the co-contaminating PHs sorb PCBs leaving them unavailable for microbial dechlorination, a critical step in the degradation and detoxification of PCBs. The goal of the proposed research is to promote PCB dechlorination by first enhancing PH biodegradation. The Underlying Operative Hypothesis of this proposal is that oxidative metabolism performed by anaerobic microorganisms will catalyze enhanced degradation of petroleum, which will result in greater bioavailability of co-contaminating PCBs for reductive dechlorination. Aerobic biodegradation of PHs would require the introduction of oxygen, which would inhibit the oxygen sensitive PCB dechlorinating bacteria. That is why this investigation is focused on the anaerobic biodegradation of the PHs. The Specific Aims for the research are driven by the following hypotheses: 1) sulfate reduction as the terminal electron accepting process (TEAP) for PH degradation will result in enhanced microbial PCB dechlorination, and 2) microbial electrode reduction as the TEAP for PH degradation will result in enhanced microbial PCB dechlorination. Sulfate can serve as a terminal electron acceptor for the anaerobic oxidation of petroleum. Microbial electrode reduction is a new and promising method that can be coupled to the degradation of organic matter and does not require the active addition of a terminal electron acceptor such as oxygen or sulfate. The PIs intend to use innovative comprehensive two-dimensional gas chromatography (GCxGC/MS) to examine the complex mixtures of PCBs and PHs. This method enables researchers to analyze components of petroleum previously not resolvable. The microbial communities will be examined with recently developed PCR based molecular technologies. This study will be the first comprehensive investigation on the anaerobic degradation of PCBs and petroleum coupled to sulfate or novel electrode reduction. It is predicted that this innovative research will lead to the development of new technologies for the co-bioremediation of PCBs and petroleum.